LED Pulsing Tests

The LED
pulsing tests were used to determine the width of the shortest pulse that can
be produced by an LED.An Avtech pulse
generator was used to send a voltage pulse through an attenuator to pulse the
LED.

A photomultiplier tube detected the emitted light and the
corresponding pulse width was measured.Data was taken for 10, 50, 100, 500, 1000 photoelectron signals (for
single photoelectron studies see SPE studies) with
the PMT set at 1900V using ~3ns voltage pulse.The data
shows that the LED can generate a pulse of at least 6ns.

A sample of the voltage pulse from
the pulse generator was view on the oscilloscope for the pulse used to produce
the 10, 50, 100 photoelectron signals and for the pulse used to produce the 500
and 1000 photoelectron signals.

The signals plotted below, show
that a small change in amplitude produces a substantial change in the number of
photoelectrons.

The conclusion is that an LED can
produce a pulse of a least 6ns and still yield up to a several hundred
photoelectron signal.The pulse width
seems to increase slightly as the number of photoelectrons exceeds ~500.However, detailed studies of this effect
were not performed and the results should be considered inconclusive for the
1000-photoelectron signals.